Traditionally, wear systems utilize external lubricants, such as oil or grease, to increase the wear resistance and to reduce frictional losses between moving contacting surfaces of components in tribological systems. However, such external lubricants often must be replaced periodically and may be unevenly distributed over the wear surface, resulting in increased cost and inefficiency of the wear system. Additionally, in some areas, such as food processing and photocopying, in which product contamination is a concern, traditional external lubricants may be undesirable.
Therefore, in many wear systems, it may be desirable to replace or eliminate external lubricants by using internal lubricants in polymeric components to improve the tribological properties (such as wear resistance and friction resistance). Internal lubricants can be used to reduce coefficients of friction between polymeric and metallic surfaces, increase wear resistance, improve flow characteristics, and enhance properties of the polymer, such as knitting and wetting. The use of an internal lubricant can either eliminate the need for an external lubricant or provide improved part life in an application that cannot tolerate an external lubricant. Commonly used internal lubricants include waxes, fatty acids, metal stearates, aramid, silicone, graphite, and molybdenum disulfide. Additionally, certain fluoropolymers are known to contribute low coefficients of friction in certain polymers. For example, polytetrafluoroethylene (PTFE), which has a very low coefficient of friction and exhibits favorable lubricant properties, is a commonly used internal lubricant for many compounds and base polymers.
However, in some systems, it may be desirable to utilize a composition free of PTFE. For example, some applications require materials which are non-halogenated, and thus PTFE should be avoided. PTFE is also known to adversely affect the impact properties of some polymer composites, which would preclude the use of such a compound in such applications in which impact strength is of increased importance. Finally, PTFE is generally more expensive than base polymers in which it is compounded, in which case the level of benefit imparted by the PTFE may not justify the added expense. However, since some level of internal lubrication may still be desirable, alternatives to PTFE are needed.
Methods for using polyolefins as internal lubricants to improve the tribological properties of various types of polymer composites are known. Such composites include polyamide/polypropylene blends and polycarbonate compositions, including polycarbonate/polyolefin blends. However, there remains a need in the art for a PTFE replacement which will function as an internal lubricant for polyphenylene ether and/or styrene-containing compositions and is demonstrated to improve the tribological properties of such compositions, yet exhibits none of the disadvantages of PTFE outlined above.